Surgical technique and neuropsychological outcome of transsylvian hippocampal transection in 26 patients with paradoxical temporal lobe epilepsy

: Considerable research has been conducted to distinguish between mesial temporal lobe epilepsy (MTLE) and non-MTLE, as defined in relation to paradoxical temporal lobe epilepsy (PTLE). Although our previous studies have indicated good memory-related outcome of transsylvian selective amygdalohippocampectomy (TSA) in patients with MTLE, the cause of postoperative decline in verbal memory remains unclear in cases of PTLE. The present study aimed to investigate the effects of transsylvian hippocampal transection (TSHT) sparing the hippocampus and unaffected brain tissue on memory function in cases of PTLE. The study population comprised 26 patients with PTLE syndrome (left, 15; right, 11). All patients underwent comprehensive neuropsychological analysis of their verbal and nonverbal memory, attention, and delayed recall preoperatively, and at 1 month and 1 year after TSHT. Separate repeated-measures multivariate analysis of variance (MANOVA) was performed for memory scores collected at these time points. In the left TSHT group, the IQ scores were maintained even at 1 year postoperatively, whereas in the right TSHT group, the IQ scores improved at 1 month and were maintained at 1 year postoperatively. Although verbal memory decreased immediately after left TSHT, this decline tended to improve to the preoperative level at 1 year postoperatively. In the right TSHT group, verbal memory, nonverbal memory, and delayed recall improved immediately after surgery and the improved was maintained even after 1 year. The results of the present study indicate that TSHT for PTLE is effective in preserving and improving memory function. In particular, TSHT showed significant preservation of verbal memory in patients with left non-hippocampal atrophy.